Omar U. Ahmed

Deep oxidative desulfurization of liquid fuels

Abstract Increase in energy demand and consumption has been accompanied by a corresponding increase in sulfur emissions. These pollutants have both health and economic consequences. Furthermore, it significantly reduces the efficiency of advanced emission control systems of diesel engines, thereby indirectly causing more harm to the environment. This resulted in stringent sulfur emission limit down to about 15 ppm or less and in turn served as an incentive for research into alternative sulfur reduction technologies. Although feasible improvements to hydrodesulfurization are currently under investigation, adsorptive, extractive, oxidative and biodesulfurization have also been studied in recent years. Oxidative desulfurization appears to be one of the most promising desulfurization technologies due to its broadness and compatibility with other technologies such as extractive, adsorptive and biodesulfurization. The advent of ionic liquids as extraction solvents has made this even more so. This work, therefore, reviews the different approaches and investigations carried out on oxidative desulfurization while identifying research gaps and giving important recommendations.

Characteristics and intermolecular interaction of eutectic binary mixtures: Reline and Glyceline

Deep Eutectic Solvents are promising greener and cheaper alternatives to ionic liquids. The applications involving these solvents depend largely on their physical and chemical properties. However, a DES may possess both desirable and undesirable properties for a certain application. In such situations, mixing two DESs, each possessing a unique set of properties, may yield one with a more suitable set of physical and chemical properties for the same application. In this work, the variation in the physical properties of Reline upon addition of Glyceline was investigated. While a positive deviation of excess molar volume was observed, a negative deviation of viscosity was recorded with the increase in Glyceline mol% indicating a disruption of the ordered structure of Reline. The highest deviation in both cases was observed at 30 mol% Glyceline. The physical properties measured were density, viscosity, pH, RI and conductivity. The Glyceline molar percentage studied was 0 to 100mol% while temperature was varied within the range of 20 °C to 80 °C.

Efficient non-catalytic oxidative and extractive desulfurization of liquid fuels using ionic liquids

Oxidative desulfurization (ODS) is one of the promising alternative and heavily researched desulfurization technologies. This is partly due to its ability to preferentially oxidize and ease the removal of refractory sulfur compounds with the aid of a suitable solvent. Despite its long list of advantages, challenges in different research areas within ODS technology still exist. In this work, an effort was made to bridge the gap that exists in terms of the selection of suitable oxidant and strategy. A preliminary kinetic modeling of the experimental data showed that the non-catalytic conversion of dibenzothiophene (DBT) and benzothiophene (BT) to their corresponding sulfones using the electrophilic meta-chloroperoxybenzoic acid (mCPBA) can be considered a bimolecular and a trimolecular reaction respectively. Using an ionic liquid (IL) as an extraction solvent in a simultaneous oxidation and extraction setup (EODS), >78% BT was removed at optimum experimental conditions. Using the post-oxidation extractive desulfurization setup (OEDS), 99% removal of BT was achieved at milder optimum experimental conditions. Also using the OEDS strategy, >99% of DBT removal was achieved after only 15 min at 60 °C, with a mass fraction of ≥0.5 and O/S of 3/1 for all the ILs tested. Finally, the sulfur content of a commercial diesel fuel was reduced to 15.6 ppm using the OEDS strategy with tetrabutylphosphonium methanesulfonate as a suitable extraction solvent, which can be readily regenerated.